Sheet for cosmetic

Abstract

To provide a cosmetic sheet which has water resistance, transparency, excellent protective effect such as trapping of harmful substances and is suitable for use for the face or the like.SOLUTION: There is provided a cosmetic sheet which contains nonionic cellulose nanofibers having an average fiber diameter of 2 to 30 nm, a polyhydric alcohol and water. The polyhydric alcohol is at least one selected from the group consisting of 1,3-butylene glycol, glycerin, pentylene glycol, propylene glycol and dipropylene glycol and the thickness is 100 μm or more and 2000 μm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a cosmetic sheet containing cellulose nanofibers.

Background Art

[0002] As a cosmetic sheet, a gel-like sheet containing a polyhydric alcohol is known for the purpose of improving moisture retention. As a gelling agent for such a gel-like sheet, a new material called cellulose nanofibers (hereinafter sometimes abbreviated as "CNF") obtained by subdividing fibers constituting a plant-derived cellulose material has attracted attention.

[0003] For example, there is a sheet-like material containing CNF, polyvalent metal ions, and a polyhydric alcohol (see, for example, Patent Document 1). The sheet-like material of Patent Document 1 is said to have high moisture retention and can be used for a long time.

[0004] In addition, there is a sheet-like material containing CNF and water (see, for example, Patent Document 2). As a cosmetic, those having a transparent appearance are preferred by consumers. However, if the fiber diameter of CNF is large or CNFs aggregate with each other, light scattering by CNF increases, and the transparency of the sheet-like material decreases. Therefore, in order to improve the transparency of the sheet, the fiber diameter of CNF in the sheet-like material of Patent Document 2 is set to 1000 nm or less.

[0005] By the way, in order to produce CNF, it is necessary to finely defibrate the cellulose material as a raw material. Even if an attempt is made to defibrate the cellulose material as it is, since it is a material in which fibers are bound by strong hydrogen bonds, a great deal of energy is required for defibrillation, and it is difficult to obtain CNF of an appropriate size.

[0006] Therefore, in Patent Documents 1 and 2, by introducing a carboxyl group or a phosphite group into cellulose, the fibers of cellulose are electrically repelled to facilitate defibrillation, and the CNF thus obtained is formed into a sheet-like material.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] Although CNF having a carboxyl group or a phosphorous acid group is easy to be refined to improve transparency, since it is obtained by modifying cellulose to impart ionic properties, it is likely to discolor over time when used as a cosmetic, and there is a risk that its physical properties may change when coexisting with various additives.

[0009] Once the functional groups are removed from CNF into which a carboxyl group or a phosphorous acid group has been introduced to return it to a non-ionic one, it is difficult. The sheet-like material of Patent Document 1 contains CNF having a carboxyl group, and the sheet-like material of Patent Document 2 contains CNF having a phosphorous acid group, and neither of them was suitable as a cosmetic.

[0010] The present invention has been made in view of the above problems, and an object thereof is to provide a cosmetic sheet that is excellent in water resistance, transparency, and skin protection effect by trapping harmful substances, and is suitable for use on the face and the like.

Means for Solving the Problems

[0011] The characteristic of the configuration of the cosmetic sheet according to the present invention for solving the above problems is that it contains non-ionic cellulose nanofibers having an average fiber diameter of 2 to 30 nm, a polyhydric alcohol, and water.

[0012] According to the cosmetic sheet of this configuration, since the cellulose nanofibers with an average fiber diameter of 2 to 30 nm are uniformly dispersed in the sheet, light scattering is suppressed and high light transmittance is obtained, and the transparency required when used on the face or the like can be improved. In addition, the non-ionic cellulose nanofibers are chemically stable, have high water resistance when used as a cosmetic sheet, have little discoloration over time, and do not react with various additives even when coexisting with them, so it becomes a product suitable for use on the face or the like.

[0013] In the cosmetic sheet according to the present invention, It is preferable that the polyhydric alcohol is at least one selected from the group consisting of 1,3-butylene glycol, glycerin, pentylene glycol, propylene glycol, and dipropylene glycol.

[0014] According to the cosmetic sheet of this configuration, when the polyhydric alcohol is at least one selected from the group consisting of 1,3-butylene glycol, glycerin, pentylene glycol, propylene glycol, and dipropylene glycol, a cosmetic sheet having appropriate flexibility and light transmittance is obtained.

[0015] In the cosmetic sheet according to the present invention, the content rate of the cellulose nanofibers is 3.5 to 25% by mass, the content rate of the polyhydric alcohol is 50 to 71.5% by mass, the mass ratio (A:B) of the content (A) of the cellulose nanofibers to the content (B) of the polyhydric alcohol is 1:2 to 1:20, and it is preferable that the water content rate is 25% or less.

[0016] According to the cosmetic sheet of this configuration, the content rate of cellulose nanofibers is 3.5 to 25% by mass, the content rate of polyhydric alcohol is 50 to 71.5% by mass, the above mass ratio (A:B) is 1:2 to 1:20, and the water content rate is 25% or less. As a result, the light transmittance, strength, and flexibility are excellent, so it is a product suitable for cosmetics used on the face and the like.

[0017] In the cosmetic sheet according to the present invention, It is preferable that the thickness is 100 μm or more and 2000 μm or less.

[0018] According to the cosmetic sheet of this configuration, since the thickness is 100 μm or more and 2000 μm or less, it becomes a product with flexibility and good usability while maintaining the strength of the film.

[0019] In the cosmetic sheet according to the present invention, It is preferable that the total light transmittance when the thickness is 100 μm is 92% or more.

[0020] According to the cosmetic sheet of this configuration, by having high light transmittance, the transparency required when used on the face and the like can be improved.

Mode for Carrying Out the Invention

[0021] Hereinafter, the cosmetic sheet of the present invention will be described in detail. However, the present invention is not intended to be limited to the embodiments and examples described below.

[0022] 〔Cosmetic Sheet〕 The cosmetic sheet of the present invention contains CNF, polyhydric alcohol, and water.

[0023] <cnf> CNF is the main material that serves as a gelling agent in the cosmetic sheet of the present invention. As the CNF, a non-ionic one with an average fiber diameter of 2 to 30 nm is used. Since the fiber diameter of microfibrils, which are the constituent units of natural cellulose, is 2 to 3 nm in higher plants, in order to make the average fiber diameter of CNF less than 2 nm, it is necessary to apply a great deal of energy to make it finer, resulting in a high manufacturing cost. On the other hand, if the average fiber diameter of CNF is made larger than 30 nm, light scattering increases, and there is a risk of a decrease in transparency. When the transparency of the cosmetic sheet decreases, when applied to cosmetics used on the face or the like, there is a risk of dullness or the like occurring and damaging the appearance. The crystal form of cellulose may be either type I or type II, but if it is type I, it is stable in solvents such as water, and when blended into cosmetics or the like, better shape retention can be imparted. Non-ionic CNF can be produced by suspending natural cellulose in water and making it finer by physical means. Also, rather than directly defibrating the cellulose material, it is easier to form it into a nanofiber state by electrostatic repulsion between fibers by introducing ionic functional groups through chemical modification. Therefore, after once performing chemical modification, it is preferable to desorb and regenerate the introduced functional groups. Examples of such chemically modified cellulose include xanthated cellulose obtained by adding carbon disulfide to alkali-treated cellulose to introduce a xanthate group (-OCSS - M + ).

[0024] Zanthated cellulose can be easily subjected to a regeneration treatment such as an acid treatment or a heat treatment to remove the zanthate group and return it to a hydroxyl group. By passing through steps such as regeneration as zanthated cellulose, impurities in the CNF can be reduced. It is desirable that the CNF used in the cosmetic sheet of the present invention has all the zanthate groups introduced by chemical modification returned to hydroxyl groups, but as long as it does not interfere with the production and use of the cosmetic sheet, some zanthate groups may remain. The content of the zanthate group in zanthated cellulose is evaluated by the average degree of zanthate substitution, which is the average number of hydroxyl groups substituted with zanthate groups per glucose unit of cellulose. In the cosmetic sheet of the present invention, the CNF preferably has an average degree of zanthate substitution of 0.01 or less, more preferably 0.005 or less. If the average degree of zanthate substitution is 0.01 or less, it exhibits the same reactivity as the unmodified one and can be suitably used in cosmetics used on the face and the like as nonionic CNF.

[0025] The content of CNF in the cosmetic sheet is preferably 3.5 to 25% by mass. If the content of CNF in the cosmetic sheet is within the above range, a cosmetic sheet having sufficient strength and excellent flexibility can be produced.

[0026] <Polyhydric alcohol> Examples of the polyhydric alcohol include diols having two or more hydroxyl groups in the molecule such as 1,3-butylene glycol, pentylene glycol, propylene glycol, and dipropylene glycol, and glycerin. These polyhydric alcohols may be used alone or as a mixture of two or more.

[0027] The content rate of polyhydric alcohol in the sheet for cosmetics is preferably 50 to 71.5 mass%. If the content rate of polyhydric alcohol in the sheet for cosmetics is within the above range, a uniform dispersion state of CNF in the sheet can be maintained, and a sheet for cosmetics excellent in moisture retention and flexibility can be obtained. Further, the mass ratio (A:B) of the content (A) of CNF and the content (B) of polyhydric alcohol in the sheet for cosmetics is preferably in the range of 1:2 to 1:20 in terms of mass ratio. If the mass ratio (A:B) in the sheet for cosmetics is within the above range, the light transmittance, strength, and flexibility of the sheet for cosmetics will be excellent, so that it can be a sheet for cosmetics suitable for cosmetics used on the face and the like.

[0028] 〔Thickness of the sheet for cosmetics〕 The sheet for cosmetics is required to have a strength that does not tear when following the movement of the skin. The thickness of the sheet for cosmetics of the present invention is preferably 100 μm or more. If the thickness is 100 μm or more, it can flexibly follow the movement of the skin while improving the strength of the film, resulting in a product with good usability. In addition, the upper limit of the thickness of the sheet for cosmetics is preferably 2000 μm or less. If the thickness exceeds 2000 μm, it becomes difficult to follow the movement of the skin and the adhesion decreases, making it difficult to attach the sheet to the skin.

[0029] 〔Light transmittance〕 The sheet for cosmetics is desired to have high light transmittance in order to obtain excellent transparency. The sheet for cosmetics of the present invention preferably has a total light transmittance of 92% or more when the thickness is 100 μm. If the total light transmittance is 92% or more, the transparency required when used on the face and the like can be improved by having appropriate light transmittance. The total light transmittance of the sheet for cosmetics can be measured, for example, using a haze meter (HM-150N, manufactured by Murakami Color Research Laboratory Co., Ltd.).

[0030] 〔Manufacture of CNF〕 The CNF derived from xanthated cellulose suitable for use in the sheet for cosmetics of the present invention can be manufactured by sequentially performing the following steps (I) to (V).

[0031] (I) Alkaline treatment of cellulose material Examples of the cellulose material include wood pulp such as kraft pulp and sulfite pulp, wood flour, biomass-derived materials such as rice straw, waste paper, paper-derived materials such as filter paper and paper powder, powdered cellulose, and cellulose processed products that retain crystallinity such as micrometer-sized microcrystalline cellulose. However, it is not limited to these examples. Among these cellulose materials, it is preferable to use wood pulp because it is easily available and inexpensive.

[0032] In the alkaline treatment of the cellulose material, the cellulose material is treated with an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to obtain alkali cellulose. The concentration of the aqueous alkali metal hydroxide solution is preferably 4% by mass or more. When the concentration of the aqueous alkali metal hydroxide solution is less than 4% by mass, the mercerization of cellulose does not proceed sufficiently, and the amount of by-products generated during subsequent xanthation becomes non-negligible, resulting in a decrease in yield.

[0033] (II) Xanthation treatment In the xanthation treatment, by reacting alkali cellulose with carbon disulfide (CS2), (-O - M + ) group is converted to (-OCSS - M + )Based on this, zanthated cellulose is obtained. The content rate of zanthate groups in zanthated cellulose is evaluated by the average degree of zanthate substitution. The average degree of zanthate substitution can be determined using the Bredee method. The procedure of the Bredee method is to weigh 1.5 g of zanthated cellulose as a solid content, and add 40 mL of saturated ammonium chloride solution (5 °C). After thoroughly mixing with a glass rod, filter and wash thoroughly with saturated ammonium chloride solution. Then, add 50 mL of 0.5 mol / L sodium hydroxide solution (5 °C) and stir, and then neutralize with 1.5 mol / L acetic acid. Thereafter, add 250 mL of ion-exchanged water and stir well, and add 10 mL of 1.5 mol / L acetic acid and 10 mL of 0.05 mol / L iodine solution. This solution is titrated with 0.05 mol / L sodium thiosulfate solution using 1 mass% aqueous starch solution as an indicator. Using the titration amount of sodium thiosulfate and the cellulose amount of the sample in the above procedure, the following formula (1): Average degree of zanthate substitution = (0.05×10×2 - 0.05×titration amount of sodium thiosulfate (mL)) / {1000 × (amount of cellulose in sample (g) / 162.1)} ···(1) The average degree of zanthate substitution is calculated according to this. The cellulose content rate in zanthated cellulose is measured as follows. First, disperse zanthated cellulose in water, add hydrochloric acid and perform a regeneration treatment. Next, filter the cellulose after the regeneration treatment, wash thoroughly, dry to absolute dryness, measure the mass of only cellulose, and calculate the cellulose content rate in zanthated cellulose.

[0034] When producing CNF used in the cosmetic sheet of the present invention, in the zanthation treatment, it is preferable that the average degree of zanthate substitution is 0.1 or more and 0.4 or less. If the average degree of zanthate substitution is less than 0.1, there is a possibility that the fibrillation treatment to be performed later cannot be sufficiently carried out. If the average degree of zanthate substitution exceeds 0.4, the hydrophilicity becomes too large, so there is a possibility of dissolution during the fibrillation treatment.

[0035] (III) Fibrillation treatment The fibrillation treatment is preferably carried out after dispersing the xanthated cellulose in water. As the method of fibrillation treatment, general methods can be used. For example, there is a method of fibrillating using a rotary homogenizer, bead mill, ultrasonic disperser, high-pressure homogenizer, disk refiner, etc.

[0036] The cellulose material requires a great deal of energy to be fibrillated as it is, but in the case of xanthated cellulose, the dispersibility is improved by the electrostatic repulsion between the fibers due to the xanthate group, so the energy required for fibrillation is extremely small and fibrillation can be carried out under relatively mild conditions.

[0037] (IV) Regeneration treatment By subjecting the xanthated CNF to regeneration treatment, regenerated CNF can be obtained. In this regeneration treatment, the xanthate group (-OCSS - M + ) is removed and changed to a hydroxyl group (-OH) to regenerate the xanthated cellulose into cellulose.

[0038] As the regeneration treatment method, there is a method of treating with an acid. The reaction of easily detaching the xanthate group and changing it to a hydroxyl group can be advanced by the acid. Examples of the acid used here include mineral acids and organic acids, and in particular, mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid are preferred.

[0039] As another regeneration treatment method, by heating the xanthated CNF, carbon disulfide can be dissociated from the molecules of the xanthated CNF and regenerated into cellulose to obtain CNF.

[0040] (V) Redispersion treatment After the regeneration treatment, compared with the xanthated CNF before regeneration, the xanthate groups have detached, so some are in an aggregated state due to hydrogen bonding and entanglement between the fibers. Therefore, a dispersion treatment is performed again on the aqueous dispersion of CNF after the regeneration treatment to obtain a CNF dispersion. Hereinafter, this dispersion treatment performed after the regeneration treatment is referred to as "redispersion treatment". For the redispersion treatment, general devices and methods used for dispersion treatment such as a rotary homogenizer, a high-pressure homogenizer, and an ultrasonic disperser can be used.

[0041] As described above, by sequentially performing the steps of (I) to (V), the average fiber diameter of the CNF derived from the xanthated cellulose obtained can be adjusted to 2 nm or more and 30 nm or less. The average fiber diameter of the CNF is measured by the following procedure. Ion-exchanged water is added to the obtained CNF to form an aqueous dispersion with a solid content concentration of 0.1% by mass, and centrifugation (12,000 G, 10 minutes) is performed using a centrifuge (manufactured by Beckman Coulter, Avanti J-251) to precipitate undispersed substances. The supernatant is further diluted with ion-exchanged water, then coated on a support film, stained with uranyl acetate, and dried on the support film to obtain a dried specimen. Using a transmission electron microscope (TEM: manufactured by JEOL Ltd., JEM-1400), observation is performed at an acceleration voltage of 120 kV. 50 nanofibers are selected from an image at 50,000 times magnification, the fiber diameter of each is measured, and the average value is obtained and taken as the average fiber diameter.

[0042] [Manufacture of Cosmetic Sheet] The cosmetic sheet of the present invention is produced by sequentially performing the following steps: (i) adding a polyhydric alcohol to an aqueous dispersion of nonionic CNF having an average fiber diameter of 2 to 30 nm to obtain a gel composition; (ii) molding the gel composition into a sheet shape; and (iii) drying the sheet-shaped gel composition. In the step (ii), examples of the method for molding the gel composition into a sheet shape include putting the gel composition into a container capable of holding the shape of the gel composition, and applying or casting the gel composition onto a smooth substrate. In the step (iii), the method for drying the sheet-shaped gel composition is not particularly limited, and examples thereof include air drying, heat drying, vacuum drying, and combinations thereof.

Example

[0043] 〔Production Example 1 of Nonionic CNF〕 Softwood bleached kraft pulp (NBKP) was weighed so that the pulp solid content was 100 g, 2500 g of an 8.5 mass% aqueous sodium hydroxide solution was added, and the mixture was stirred at room temperature for 3 hours for alkali treatment. After this alkali treatment, the pulp was subjected to solid-liquid separation to obtain a dehydrated product of alkali cellulose.

[0044] The dehydrated product of alkali cellulose prepared above was weighed so that the pulp solid content was 100 g, 35 g of carbon disulfide (35 mass% based on the pulp solid content) was added, and the sulfidation reaction was allowed to proceed for xanthation treatment to obtain xanthated cellulose.

[0045] The above xanthated cellulose was weighed so that the pulp solid content was 10 g, ion-exchanged water was added for dispersion, solid-liquid separation was performed, and it was thoroughly washed with ion-exchanged water. All of the washed xanthated cellulose was recovered, and ion-exchanged water was added to obtain 2 kg of an aqueous suspension having a cellulose concentration of 0.5 mass%. This aqueous suspension was passed through a high-pressure homogenizer three times at a pressure of 80 MPa for fibrillation treatment to obtain xanthated CNF. The average degree of xanthate substitution of the obtained xanthated CNF was 0.263, the fiber diameter was 3.0 to 7.4 nm, and the average fiber diameter was 6.1 nm.

[0046] To 1.5 kg of the aqueous suspension of zanthate CNF (cellulose concentration: 0.5% by mass) obtained by the above procedure, 33 mL of 1 mol / L sulfuric acid was added, and a regeneration treatment was performed. After the treatment, it was neutralized to pH 7 with a 1 mol / L sodium hydroxide solution to obtain an aqueous suspension of regenerated CNF. When the average degree of zanthate substitution was measured, it was less than 0.001, which is the lower limit of measurement. Thus, it was confirmed that the zanthate groups had almost completely detached and reverted to hydroxyl groups by the acid treatment.

[0047] The aqueous suspension of the regenerated CNF obtained above was centrifuged using a centrifuge while adding ion-exchanged water for thorough washing. All of the washed regenerated CNF was recovered, ion-exchanged water was added to make 1 kg of an aqueous dispersion with a solid content concentration of 1.0% by mass of CNF, and re-dispersion treatment was performed at a pressure of 80 MPa using a high-pressure homogenizer to obtain non-ionic CNF as Production Example 1. After the re-dispersion treatment, when the average fiber diameter of the re-dispersion of the regenerated CNF was calculated, the fiber diameter was 3.0 to 7.4 nm, and the average fiber diameter was 6.0 nm.

[0048] 〔Production Example 2 of Non-ionic CNF〕 The re-dispersion of the regenerated CNF (average fiber diameter: 6.0 nm) obtained in Production Example 1 above was diluted to a solid content concentration of 0.5% by mass, and centrifuged (75000 G, 10 minutes) using a centrifuge (manufactured by Beckman Coulter, Avanti J-251). The centrifuged supernatant was recovered and concentrated to a solid content concentration of 1.0% by mass using an evaporator. When the average fiber diameter of the regenerated CNF in the centrifuged supernatant was calculated, the fiber diameter was 2.0 to 3.1 nm, and the average fiber diameter was 2.6 nm.

[0049] 〔Production Example 3 of Non-ionic CNF〕 Zanthate CNF with an average zanthate substitution degree of 0.264, a fiber diameter of 2.0 to 51.4 nm, and an average fiber diameter of 28.1 nm was obtained in the same manner as above, except that the number of passes of the aqueous suspension of the zanthate cellulose of Production Example 1 through the high-pressure homogenizer was changed to 2 for defibrillation treatment.

[0050] This zantate CNF was processed in the same manner as in Production Example 1 to obtain a redispersion of nonionic CNF having a fiber diameter of 2.0 to 50.7 nm and an average fiber diameter of 28.0 nm.

[0051] <Production and Evaluation of Cosmetic Sheets> Cosmetic sheets (Examples 1 to 4) of the present invention were produced, and the hardness was measured, and the shape retention and water resistance were evaluated. Further, for comparison, cosmetic sheets (Comparative Examples 1 to 3) outside the scope of the present invention were produced, and the same measurements and evaluations were performed.

[0052] [Example 1] Ion-exchanged water and 1,3-butylene glycol (BG) as a polyhydric alcohol were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and after adjusting so that the content of CNF was 0.5% by mass and the content of 1,3-butylene glycol was 5% by mass at the final concentration, it was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation) to obtain a gel-like composition. This gel-like composition was transferred to a plastic petri dish so that the cellulose amount was 28.5 g / m 2 and dried by evaporating water with a blow dryer at 50°C for 15 hours. A cosmetic sheet of Example 1 having a CNF content of 6.8% by mass, a 1,3-butylene glycol content of 68.2% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:10, and a water content of 25% was obtained.

[0053] [Example 2] In Example 1, the CNF in the gel-like composition was changed to the CNF of Production Example 2 (average fiber diameter 2.6 nm). Otherwise, in the same manner as in Example 1, a cosmetic sheet of Example 2 having a CNF content of 6.8% by mass, a 1,3-butylene glycol content of 68.2% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:10, and a water content of 25% was obtained.

[0054] [Example 3] In Example 1, the CNF in the gel composition was changed to the CNF of Production Example 3 (average fiber diameter: 28.0 nm). Otherwise, in the same manner as in Example 1, a cosmetic sheet of Example 3 was obtained, wherein the CNF content was 6.8% by mass, the 1,3-butylene glycol content was 68.2% by mass, the mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) was 1:10, and the water content was 25%.

[0055] [Example 4] In Example 1, the content of 1,3-butylene glycol in the gel composition was adjusted to 10% by mass. Otherwise, in the same manner as in Example 1, a cosmetic sheet of Example 4 was obtained, wherein the CNF content was 3.5% by mass, the 1,3-butylene glycol content was 71.5% by mass, the mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) was 1:20, and the water content was 25%.

[0056] [Comparative Example 1] In Example 1, the gel composition did not contain 1,3-butylene glycol, and the CNF content was adjusted to 0.5% by mass. Otherwise, in the same manner as in Example 1, a cosmetic sheet of Comparative Example 1 with a water content of 25% was obtained.

[0057] [Comparative Example 2] In Example 1, xanthan gum (KELTROL CG-T, manufactured by Sankyo Co., Ltd.) was used instead of CNF. Otherwise, in the same manner as in Example 1, a cosmetic sheet of Comparative Example 2 was obtained, wherein the xanthan gum content was 6.8% by mass, the 1,3-butylene glycol content was 68.2% by mass, the mass ratio (A:B) of the xanthan gum content (A) to the 1,3-butylene glycol content (B) was 1:10, and the water content was 25%.

[0058] [Comparative Example 3] To an aqueous dispersion of mechanically fibrillated CNF (manufactured by Sugino Machine Limited: BiNFi-sWMa-10002, fiber diameter 24.1 to 53.2 nm, average fiber diameter 31 nm), ion-exchanged water and 1,3-butylene glycol (BG) as a polyhydric alcohol were added. After adjusting to a final concentration such that the CNF content was 0.5% by mass and the 1,3-butylene glycol content was 5% by mass, stirring was performed at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation) to obtain a gel-like composition. This gel-like composition was transferred to a plastic petri dish so that the cellulose amount was 28.5 g / m 2 and dried by evaporating water for 15 hours using a forced-air dryer at 50 °C to obtain a cosmetic sheet for Comparative Example 3 with a CNF content of 6.8% by mass, a 1,3-butylene glycol content of 68.2% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:10, and a water content of 25%.

[0059] <Hardness> The hardness of the cosmetic sheet was measured using a rubber / plastic hardness meter (Durometer GS-701N, manufactured by TECLOCK). When the measured value by the rubber / plastic hardness meter is less than 20, the cosmetic sheet is too soft and difficult to handle. When the measured value is 20 or more and less than 40, the cosmetic sheet is neither too soft nor too hard and is easy to handle. When the measured value is 40 or more, the cosmetic sheet is easy to handle but too hard to adhere to the skin.

[0060] <Shape retention> The change in shape when the cosmetic sheet was pinched with a finger and the presence or absence of resilience to bending deformation were observed to evaluate the shape retention of the cosmetic sheet. Regarding the resilience to bending deformation, those that did not break when the cosmetic sheet was bent 180° were considered to have resilience. The evaluation criteria for shape retention were as follows. 〇: The sheet shape can be maintained even when pinched with a finger, and there is resilience to bending deformation. △: The sheet form can be maintained even when pinched with a finger, but there is no resilience to bending deformation. ×: A viscous or fluid gel that cannot maintain a sheet shape when pinched with fingers.

[0061] <Water resistance> The mass of the cosmetic sheet was measured, and then it was immersed in ion-exchanged water and left standing at 50 °C for 20 hours. Twenty hours after the immersion, it was observed whether the cosmetic sheet dissolved. If it did not dissolve, the cosmetic sheet was taken out and its mass was measured, and the following formula (2): Mass change rate (%) = (Mass after immersion (g) / Mass before immersion (g)) × 100 ···(2) was used to calculate the mass change rate.

[0062] <Thickness> The thickness of the cosmetic sheet was measured by observing the cross-section of the sheet cut with a cutter using a digital microscope (VH-X100, manufactured by KEYENCE).

[0063] Table 1 shows the manufacturing conditions, hardness, shape retention, water resistance, and thickness of the cosmetic sheets of Examples 1 to 4 and Comparative Examples 1 to 3.

[0064]

Table 1

[0065] The cosmetic sheets of Examples 1 to 4 all became uniform films without the separation of 1,3-butylene glycol after the drying of the gel composition, and had an appropriate hardness (softness) with a measured value by a rubber / plastic hardness tester of 20 or more and less than 40, and shape retention. Also, it was confirmed that the cosmetic sheets of Examples 1 to 4 did not dissolve even 20 hours after immersion in ion-exchanged water and had high water resistance. The weight change rate 20 hours after immersion was 100 to 129%.

[0066] On the other hand, the cosmetic sheet of Comparative Example 1 that does not contain a polyhydric alcohol became a non-uniform film after drying, was hard and had no resilience against bending deformation, and the film cracked. In the cosmetic sheet of Comparative Example 2 that does not contain CNF, 1,3-butylene glycol separated after drying of the gel composition. Further, it was confirmed that the cosmetic sheet of Comparative Example 2 dissolved by immersion in ion-exchanged water and did not have water resistance. The cosmetic sheet of Comparative Example 3 using mechanically defibrated CNF had good water resistance and shape retention, but lacked softness and did not form a uniform film after drying.

[0067] Next, cosmetic sheets of the present invention (Examples 5 to 11) were prepared and their light transmittance was evaluated. For comparison, cosmetic sheets outside the scope of the present invention (Comparative Examples 4 and 5) were prepared and the same evaluation was carried out.

[0068] 〔Examples 5-1, 5-2, and 5-3〕 Ion-exchanged water and 1,3-butylene glycol (BG) as a polyhydric alcohol were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and after adjusting so that the content rate of CNF was 0.5 mass%, the content rate of 1,3-butylene glycol was 1 mass%, 5 mass%, and 10 mass% at the final concentration, each was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation) to obtain three kinds of gel compositions. Each gel composition had a cellulose amount of 28.5 g / m 2 Transfer it to a plastic petri dish so that it becomes, and evaporate and dry the moisture with a hot air dryer at 50 °C for 15 hours. The cosmetic sheet of Example 5-1 has a CNF content of 25% by mass, a 1,3-butylene glycol content of 50% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:2, and a water content of 25%. The cosmetic sheet of Example 5-2 has a CNF content of 6.8% by mass, a 1,3-butylene glycol content of 68.2% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:10, and a water content of 25%. Also, the cosmetic sheet of Example 5-3 has a CNF content of 3.6% by mass, a 1,3-butylene glycol content of 71.5% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:20, and a water content of 25% was obtained.

[0069] 〔Example 6〕 Ion-exchanged water and propylene glycol (PG) as a polyhydric alcohol were added to the aqueous dispersion of CNF (average fiber diameter 6.0 nm) of Production Example 1, and after adjusting to a final concentration such that the CNF content was 0.5% by mass and the propylene glycol content was 10% by mass, it was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII2.5 type, manufactured by Primix Corporation) to obtain a gel-like composition. This gel-like composition was transferred to a plastic petri dish so that the cellulose amount was 28.5 g / m 2 and evaporated and dried the moisture with a hot air dryer at 50 °C for 15 hours to obtain a cosmetic sheet of Example 6 having a CNF content of 3.6% by mass, a propylene glycol content of 71.5% by mass, a mass ratio (A:B) of the CNF content (A) to the propylene glycol content (B) of 1:20, and a water content of 25%.

[0070] 〔Example 7〕 As the polyhydric alcohol, pentylene glycol (PeG) was used instead of propylene glycol. Otherwise, in the same manner as in Example 6, a cosmetic sheet of Example 7 was obtained, in which the CNF content rate was 3.6% by mass, the pentylene glycol content rate was 71.5% by mass, the mass ratio (A:B) of the CNF content (A) to the pentylene glycol content (B) was 1:20, and the water content rate was 25%.

[0071] [Example 8] As the polyhydric alcohol, glycerin (GLY) was used instead of propylene glycol. Otherwise, in the same manner as in Example 6, a cosmetic sheet of Example 8 was obtained, in which the CNF content rate was 3.6% by mass, the glycerin content rate was 71.5% by mass, the mass ratio (A:B) of the CNF content (A) to the glycerin content (B) was 1:20, and the water content rate was 25%.

[0072] [Example 9] As the polyhydric alcohol, a 1:1 mixture of 1,3 - butylene glycol (BG) and glycerin (GLY) was used instead of propylene glycol. Otherwise, in the same manner as in Example 6, a cosmetic sheet of Example 9 was obtained, in which the CNF content rate was 3.6% by mass, the content rate of the mixture of 1,3 - butylene glycol and glycerin was 71.5% by mass, the mass ratio (A:B) of the CNF content (A) to the content of the mixture of 1,3 - butylene glycol and glycerin (B) was 1:20, and the water content rate was 25%.

[0073] [Example 10] In Example 5 - 3, the CNF in the gel - like composition was changed to the CNF of Production Example 2 (average fiber diameter 2.6 nm). Otherwise, in the same manner as in Example 5 - 3, a cosmetic sheet of Example 10 was obtained, in which the CNF content rate was 3.6% by mass, the 1,3 - butylene glycol content rate was 71.5% by mass, the mass ratio (A:B) of the CNF content (A) to the 1,3 - butylene glycol content (B) was 1:20, and the water content rate was 25%.

[0074] [Example 11] In Example 5-3, the CNF in the gel composition was changed to the CNF of Production Example 3 (average fiber diameter: 28.0 nm). Otherwise, in the same manner as in Example 5-3, a cosmetic sheet of Example 11 was obtained, in which the CNF content was 3.6% by mass, the content of 1,3-butylene glycol was 71.5% by mass, the mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) was 1:20, and the water content was 25%.

[0075] [Comparative Example 4] Ion-exchanged water and 1,3-butylene glycol (BG) as a polyhydric alcohol were added to an aqueous dispersion of mechanically defibrated CNF (manufactured by Sugino Machine Limited: BiNFi-sWMa-10002, average fiber diameter: 31 nm), and after adjusting to a final concentration such that the CNF content was 0.5% by mass and the content of 1,3-butylene glycol was 5% by mass, the mixture was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII2.5 type, manufactured by Primix Corporation) to obtain a gel composition. This gel composition was transferred to a plastic petri dish so that the cellulose amount was 28.5 g / m 2 and dried by evaporating water for 15 hours using a blower dryer at 50°C to obtain a cosmetic sheet of Comparative Example 4, in which the CNF content was 6.8% by mass, the content of 1,3-butylene glycol was 68.2% by mass, the mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) was 1:10, and the water content was 25%.

[0076] [Comparative Example 5] In Example 6, ethanol (EtOH), a monohydric alcohol, was used instead of propylene glycol, a polyhydric alcohol. Otherwise, in the same manner as in Example 6, a cosmetic sheet of Comparative Example 5 was obtained, in which the CNF content was 3.6% by mass, the ethanol content was 71.5% by mass, the mass ratio (A:B) of the CNF content (A) to the ethanol content (B) was 1:20, and the water content was 25%.

[0077] [Light transmittance] The light transmittance of the cosmetic sheet (Examples 5 to 11) of the present invention was determined by sandwiching the cosmetic sheet between glass plates and irradiating the entire visible light wavelength with a haze meter (HM-150N, manufactured by Murakami Color Research Laboratory Co., Ltd.), and using the ratio of the total transmitted light (total light transmittance) as an index. Also, the total light transmittance was similarly determined for the cosmetic sheets (Comparative Examples 4 and 5) outside the scope of the present invention.

[0078] <Thickness> The thickness of the cosmetic sheet was measured by observing the cross-section of the sheet cut with a cutter using a digital microscope (VH-X100, manufactured by KEYENCE).

[0079] Table 2 shows the total light transmittance and thickness of the cosmetic sheets of Examples 5 to 11, Comparative Examples 4 and 5. In Table 2, the cosmetic sheets of Examples 5-1, 5-2, and 5-3 are shown together as Example 5. Also, Table 2 shows the total light transmittance and thickness of the cosmetic sheet with a polyhydric alcohol content of 0% by mass.

[0080]

Table 2

[0081] As shown in Table 2, in the cosmetic sheets of Examples 5 to 11, when the polyhydric alcohol content in the cosmetic sheet was 50% by mass or more, the thickness was 100 μm or more and the total light transmittance was 92% or more. Also, in the cosmetic sheets of Examples 5-1, 5-2, and 5-3, the greater the content of 1,3-butylene glycol, the greater the film thickness, but the light transmittance tended to improve. On the other hand, in the cosmetic sheet of Comparative Example 4, compared with Examples 5-2 and 6, the thickness was about the same, but the total light transmittance decreased significantly. In the cosmetic sheet of Comparative Example 5, the film became non-uniform like the cosmetic sheet with a polyhydric alcohol content of 0% by mass, and the sheet itself was hard and had no resilience to bending deformation.

[0082] <Harmful substance trapping effect> A cosmetic sheet of the present invention (Example 12) was prepared, and a permeation test of tobacco smoke was conducted as a harmful substance. An aldehyde compound contained in tobacco smoke was used as an index of permeation. In the permeation test, the prepared cosmetic sheet was sandwiched between a perforated aluminum plate and a silicone packing, and a plate sandwiching the cosmetic sheet was placed on the well of a 24-well plate containing 1 mL of pure water. This 24-well plate was placed in a sealed container into which the smoke of two cigarettes was introduced, and the aldehyde compound in the pure water in the well after standing for 1 hour was detected. The aldehyde compound was reacted with 25 μM NBD-hydrazine in the dark for 30 minutes in the presence of 0.5 mass% trifluoroacetic acid, and the fluorescence intensity (Ex: 360 nm / Em: 450 nm) was measured with a microplate reader (Spectra Max Gemini, manufactured by Molecular Devices). The ratio of this fluorescence intensity to the blank corresponded to the amount of the aldehyde compound adsorbed on the cosmetic sheet, and the permeation rate of the aldehyde compound that permeated through the cosmetic sheet was calculated and used as an index of the harmful substance trapping effect.

[0083] 〔Examples 12-1, 12-2, and 12-3〕 To the aqueous dispersion of CNF (average fiber diameter: 6.0 nm) of Production Example 1, ion-exchanged water and 1,3-butylene glycol (BG) as a polyhydric alcohol were added, and after adjusting so that the content rate of CNF was 0.5% by mass, and the content rates of 1,3-butylene glycol were 1% by mass, 5% by mass, and 10% by mass at the final concentration, each was stirred at 3,000 rpm for 5 minutes using a homomixer (Homomixer MARKII 2.5 type, manufactured by Primix Corporation) to obtain three gel-like compositions. 1 mL of each gel-like composition was dropped onto a membrane filter (10 μm JH, manufactured by Merck Millipore), and water was evaporated and dried with a blow dryer at 50°C for 15 hours, to obtain a cosmetic sheet of Example 12-1 having a CNF content rate of 25% by mass, a 1,3-butylene glycol content rate of 50% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:2, and a water content rate of 25%, a cosmetic sheet of Example 12-2 having a CNF content rate of 6.8% by mass, a 1,3-butylene glycol content rate of 68.2% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:10, and a water content rate of 25%, and a cosmetic sheet of Example 12-3 having a CNF content rate of 3.6% by mass, a 1,3-butylene glycol content rate of 71.5% by mass, a mass ratio (A:B) of the CNF content (A) to the 1,3-butylene glycol content (B) of 1:20, and a water content rate of 25%.

[0084] Table 3 shows the permeation rates of the aldehyde compounds of the cosmetic sheets of Examples 12-1, 12-2, and 12-3. In Table 3, it is represented as a percentage with "without sheet" in which the sheet is not formed on the membrane filter being 100%. For comparison, the permeation rate of the aldehyde compound of a cosmetic sheet having a polyhydric alcohol content rate of 0% by mass is also shown.

[0085]

Table 3

[0086] As shown in Table 3, in the cosmetic sheets of Examples 12-1, 12-2, and 12-3, when the content of 1,3-butylene glycol in the cosmetic sheet was 50% by mass or more, the permeation rate of the aldehyde compound was 66% or less. In particular, in the cosmetic sheet of Example 12-3 in which the content of 1,3-butylene glycol was 71.5% by mass, the permeation rate of the aldehyde compound was 30% or less, and it was confirmed that it had an excellent harmful substance trapping effect.

Industrial Applicability

[0087] The cosmetic sheet of the present invention is excellent in water resistance, transparency, and skin protection effects by trapping harmful substances, and can be used for cosmetic applications on the face and the like, medical applications for covering wounds and the like.< / cnf>

Claims

1. A nonionic cellulose nanofiber having an average fiber diameter of 2 to 30 nm, a polyhydric alcohol, and water, with a thickness of 100 μm or more and 2000 μm or less, A cosmetic sheet having a total light transmittance of 92% or more when the thickness is 100 μm.

2. The cosmetic sheet according to claim 1, wherein the polyhydric alcohol is at least one selected from the group consisting of 1,3-butylene glycol, glycerin, pentylene glycol, propylene glycol, and dipropylene glycol.

3. The content of the cellulose nanofiber is 3.5 to 25% by mass, the content of the polyhydric alcohol is 50 to 71.5% by mass, the mass ratio (A:B) of the content (A) of the cellulose nanofiber to the content (B) of the polyhydric alcohol is 1:2 to 1:20, The cosmetic sheet according to claim 1 or 2, having a water content of 25% or less.

Images